Molecular detection based on the interaction of a receptor molecule and a target molecule is the basis of chemical and biological sensing. Given a molecular recognition system, however, digital transduction is the primary challenge of sensor design. Molecular interactions may change electronic, optical or acoustic properties of a sample.
Molecular interactions may modulate the scattering, fluorescence, absorption or other properties of a sample under test. Typically theses properties are monitored by placing a sample carrier in a conventional spectrometer or similar instrument. The sample carrier is typically a surface functionalized with molecular recognition agents. Sensitivity is increased by making the area of the functionalized surface as large as possible.
For a number of reasons, detection of absorption or spectral scattering features from surface interactions is difficult with conventional spectrometers. For example, the absorption features are typically weak. Further, isolation from strong background signals is not achieved.
In addition, conventional spectroscopic sensors are not well adapted to integration of spectral signals from large area samples. For example, when working with highly scattering diffuse samples or when using low light techniques such as fluorescence and Raman scattering, conventional grating-based spectrometers that use slits produce less than desirable measurement sensitivity, specificity, and selectivity.
Further, conventional slit-based spectrometers are not well suited for the large chemical interaction areas that are used in chemical and biological sensing. From a chemical and biological sensing perspective, a large surface area increases an effective volume of sample tested by maximizing a chemical interaction area. However, large surface areas are difficult to cover using conventional slit-based spectrometers.